passive crossovers (specifically from a 650e)

J

Jeff Kenney

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Mar 4, 2013
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I've run into an interesting/frustrating problem.

I have a client with a bunch of 650e's that were modded from stagepin to nl8. We stupidly did not check to see if the boxes did more than play what they were supposed to sound like before taking on this project. (in biamp mode with a terrible setup)

1. Do the crossovers do anything when the box is in tri-amp mode? The reason I ask is we are installing a ux3600 on the system and the boxes do not sound good. I've never put a 3600 on a 650e - altho I own some 650z's that sound amazing with them. Yes its set up right (unless there is a problem with a brand new 3600 which seems to work and has greyboxes loaded correctly) I could double check with a 8800 we have in inventory I supposed but I don't think that is the problem. Speakers sound weak.. the box sounds all wrong.. I checked my pinout 10 times because it really sounded like the hf and mf were crossed. So with all this being said if the crossover does nothing in triamp mode I can simply bypass it to output because I suspect there is a problem in the cabinet wiring.

2. If the wiring is botched what should I do? I don't see any easy way to take down the arrays, open up the cabinets, and try and fix the problem. That would probably cost more than selling the client a new pa. And trust me when they barely can afford some time and new processing/amps.. the last thing they want to do is buy a new P.A.

I've tried to look if the xovers can be removed easily with the boxes in the air. But I think with this cabinet design the xover is located in the belly behind the 15" and hf. There is no access panel - you pretty much have to disassemble the LF and HF assembly to get to it. All of this is rather difficult with no lift capabilities in the area but probably possible with a scaff buildup. I've dabbled with Xovers in the past but these things are way to complicated for me - and I am not capable of on site repair if they needed it.
 
Re: passive crossovers (specifically from a 650e)

If the internal cabinet wiring is in question, is it possible to measure from the amplifier end of the cabling and figure out which cable pair goes to what driver? You may be able to correct the pinouts at the amp end. Otherwise, in triamp mode, if the crossover is still in circuit I suspect it's just doing phase alignment or something similar.
 
Re: passive crossovers (specifically from a 650e)

One quick and easy way would be take a simple DC RESISTANCE from the amp end of the wire.

Disconnect the speaker wires.

If the crossovers are still in circuit you will get the following:

On the mid and high sections of the cabinet- you should read an open or infinite resistance.

This is because there will be a series capacitor (to knock down the lows) and it will not pass DC.

An IMPEDANCE meter will still pass the signal-because it is AC.
 
Re: passive crossovers (specifically from a 650e)

Ivan Beaver said:
One quick and easy way would be take a simple DC RESISTANCE from the amp end of the wire.

Disconnect the speaker wires.

If the crossovers are still in circuit you will get the following:

On the mid and high sections of the cabinet- you should read an open or infinite resistance.

This is because there will be a series capacitor (to knock down the lows) and it will not pass DC.

An IMPEDANCE meter will still pass the signal-because it is AC.
Click to expand...


I never thought of that Ivan! Great Idea!
 
Re: passive crossovers (specifically from a 650e)

Jeff Kenney said:
I never thought of that Ivan! Great Idea!
Click to expand...

Or you could just hook a battery up and see if you get a pop. The Cap would block the battery voltage.
HOWEVER, if you short the speaker wires together after you have hooked up the battery (and removed it), you could get a little pop/snap. This would be due to the fact that you charged up the cap with the battery-and now you have completed the circuit so the voltage goes to the driver.
 
Re: passive crossovers (specifically from a 650e)

Ivan Beaver said:
Or you could just hook a battery up and see if you get a pop. The Cap would block the battery voltage.
HOWEVER, if you short the speaker wires together after you have hooked up the battery (and removed it), you could get a little pop/snap. This would be due to the fact that you charged up the cap with the battery-and now you have completed the circuit so the voltage goes to the driver.
Click to expand...

I believe you could resolve this by strapping a resistor across those leads instead of shorting them, right? Something along the order of 1KOhm 1/4 Watt should be easily available and should get the job done.

The goal here is to bleed off the voltage slowly rather than just dumping it instantly, so the value really doesn't matter that much.

I'm curious about just hooking the wire pairs, one at a time, up to an amplifier and playing a little pink noise at low volume. You may want to roll off the bottom end depending on how loud you want to turn it up.
 
Re: passive crossovers (specifically from a 650e)

Josh Millward said:
I believe you could resolve this by strapping a resistor across those leads instead of shorting them, right? Something along the order of 1KOhm 1/4 Watt should be easily available and should get the job done.

The goal here is to bleed off the voltage slowly rather than just dumping it instantly, so the value really doesn't matter that much.

I'm curious about just hooking the wire pairs, one at a time, up to an amplifier and playing a little pink noise at low volume. You may want to roll off the bottom end depending on how loud you want to turn it up.
Click to expand...
Yes you could bleed it off, but the pop will not cause a problem.

I just mentioned it because it is something that will happen and confuse people when they have never heard it before.

"How does it pop AFTER the battery has been removed----".
 
Feel like I'm a tiny bit late to this one... but if the speakers are in the air and wires/amps are on the ground, I've had luck running high passed pink noise at low level directly to the amps to identify low/mid/hi lines from a loose bundle. With 650's I'd want to identify the low first and tag it. From there the unprocessed mid will have a distinct "shawww" with pink noise and the hi will have a distinct "ssshhhh" with unprocessed pink. Once the lines to the drivers are tagged, if using a 3600 I'd build 3 band passed outputs with lots of overlap and 6dB slopes. (like 40hz to 800hz low, 200hz to 2khz mid, 500z hi, all 6dB slopes.) Starting with the low I'd add the mid, match the volume, flip the polarity on the mid, delay the low for the most null, then flip back to normal, then do the same for mid and high. If the overlap nulls at normal and sums at inverted polarity then you can swap your speaker cables at the amp and verify it nulls with polarity inverted.

All of this is to simply verify the low, mid and hi lines are going to the correct drivers and polarity at the amp is correct.

At that point you can load the greybox and if the cabinet works, it should sound the way its supposed to. If the crossover has the famous EAW dried up electrolytic caps or burnt/broken resistors or was rewired by a chimpanzee, then it will never sound right until those are fixed. I've repaired/recapped way to many EAW crossovers... but never in the air! EAW was always good about sending schematics to me for crossovers.
 
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